In this work, the influence of the "ageing" temperature on the location and regeneration behaviour of the coke obtained in the cracking of LDPE in the presence of HZSM-5 and USY zeolites is studied. The coke content in the zeolites is influenced by the thermal treatment, and for both zeolites studied, the higher the final cracking temperature the lower the coke content. The nitrogen adsorption isotherms have shown the different deactivation mechanisms, related to the possible different locations of the coke on each zeolite and the influence of the final cracking temperature on these parameters. The regeneration study of the coked zeolites has shown that the coke combustion process strongly depends on the insoluble content of the coke (i.e., of the presence of bulky polyaromatic compounds) and of the zeolite framework. (c) 2007 Published by Elsevier B.V.